undef beats zero. Fix this missed optimization opportunity. Patch by Matt Elder!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@59705 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Analysis/ConstantFolding.cpp b/lib/Analysis/ConstantFolding.cpp
index 9f94ee3..597eecc 100644 (file)
--- a/lib/Analysis/ConstantFolding.cpp
+++ b/lib/Analysis/ConstantFolding.cpp
@@ -281,7 +281,7 @@ static Constant *FoldBitCast(Constant *C, const Type *DestTy,
 Constant *llvm::ConstantFoldInstruction(Instruction *I, const TargetData *TD) {
   if (PHINode *PN = dyn_cast<PHINode>(I)) {
     if (PN->getNumIncomingValues() == 0)
-      return Constant::getNullValue(PN->getType());
+      return UndefValue::get(PN->getType());
 
     Constant *Result = dyn_cast<Constant>(PN->getIncomingValue(0));
     if (Result == 0) return 0;